The invention relates to improvements in apparatus for manipulating stacks of overlapping sheets which are made of paper, metal, plastic, cardboard and/or other material. More particularly, the invention relates to improvements in apparatus which can be used with advantage to convert larger stacks of superimposed paper sheets or the like into smaller stacks and to advance the smaller stacks for processing in one or more additional treating apparatus. Still more particularly, the invention relates to improvements in apparatus which can be used with advantage to convert large stacks or piles into smaller stacks and to thereupon treat the smaller stacks, especially to subdivide smaller stacks into still smaller accumulations of overlapping sheets.
Apparatus of the class to which the present invention pertains are disclosed, for example, in a German-language publication entitled "POLAR Information 18" which was published by the West German firm A. Mohr Maschinenfabrik in 1985. Example 1 in this publication shows an apparatus wherein a pile of large sheets (made of paper, cardboard, paperboard, plastic material or the like) is accumulated on a vertically movable table and a pusher is employed to shift the pile sideways off the table and on to a cutting device. The pile comes to rest on a first or inlet section of a support for sheets at the cutting station, and such inlet section is located behind a hold-down device which presses upon the top sheet of the pile adjacent the cutting plane wherein a guillotine type knife is caused to descend and to subdivide the pile. The inlet section of the support is a stationary platform. In order to allow for ready shifting of piles, the table as well as the inlet section of the support in the apparatus which is disclosed in the German publication are provided with outlet openings for compressed air currents which form a cushion beneath the lowermost sheet of the pile. The arrangement is such that each opening contains a valving element which is depressed by the pile of sheets and permits compressed air to escape in order to form a layer of gaseous fluid beneath the lowermost sheet. The just described apparatus functions quite satisfactorily if the table and/or the inlet section of the support carries a single pile or stack of sheets. However, satisfactory manipulation of stacks is much more difficult if the table and/or the inlet section of the support is called upon to simultaneously support several stacks. Thus, the stacks are likely to move relative to each other during sidewise movement from the table onto the inlet section and/or during movement along the inlet section. This renders it necessary to orient the stacks with a very high degree of accuracy prior to cutting. The problem is especially acute if the stacks are so small that their lowermost sheets are acted upon by relatively small numbers of air currents or if their dimensions are such that they are temporarily totally out of register with air discharging openings or overlie only a single opening or a portion of a single opening.
It is further known to accumulate several piles or stacks of large sheets one above the other with the interposition of so-called air discharging boards. The boards can be moved to the level of the cutting machine and each thereof is provided with a large number of outlet openings for compressed air so as to ensure that a pile on the board can be shifted with the exertion of a relatively small effort. Reference may be had to publication No. ND 531203023d entitled "Polar-Luftbrettanlage" (published by A. Mohr Maschinenfabrik). The boards can further serve as a means for transporting stacks or piles of overlapping sheets subsequent to stacking.
Certain treatments of stacked sheets, such as bundling or baling, stamping or embossing, cutting and/or others, necessitate a highly accurate orientation of stacks prior to and during treatment. As a rule, a stack which has been delivered in an orientation that deviates considerably from the desired or necessary orientation cannot be readily caused to assume such desired orientation, i.e., it is desirable and advantageous to ensure that the treating station receive stacks in positions close to or practically coinciding with desired or optimum orientations. This saves time and reduces the likelihood of defacing of and/or other damage to the sheets of stacks which are on their way toward the treating station and must assume predetermined positions not later than at the start of a treatment, such as cutting, baling, embossing or the like.